X-RAY EFFECTS ON MITOTIC ACTIVITY OF THE ACCESSORY SEX ORGANS OF CASTRATE RATS STIMULATED BY TESTOSTERONE PROPIONATE

¹ Department of Genetics, Iowa State College, Ames, Iowa

1. The accessory organs of castrated male rats have been used in a study of the effects of x-rays on mitosis in somatic tissues.

2. Animals nine weeks old were castrated and the organs allowed to regress for 20 days prior to use. Half the animals received daily injections of 500 µg of testosterone propionate (in oil) until death; the others, in addition to the hormone injections, were exposed to a single dose of 320 r of x-rays, the irradiation being given at the time of the first hormone injection. Pairs of animals were killed at 24, 48, 60 and 72 hours following the irradiation and/or initial hormone treatment.

3. The response to the treatments was followed by means of mitotic index determinations and cytophotometric measurements of the DNA-Feulgen content of interphase nuclei.

4. The cytological data indicate the existence of a difference in response between the epithelium of the seminal vesicle and of the dorsal prostate. At no time during the experiment did the mitotic activity of the latter rise to levels characteristic of the former. In addition, the time-response curves for the two organs indicate that the dorsal prostate responds more slowly than the seminal vesicle.

5. The DNA-Feulgen measurements together with the mitotic index data indicate that in the controls and in the experimental animals killed prior to 48 hours there is a close correspondence between the level of mitotic activity and the rate of chromosomal reduplication. Over the period of 48-72 hours in the case of the dorsal prostate the data show that, during the time of maximal hormonal stimulation, DNA synthesis is proceeding at a rate appreciably faster than the rate at which nuclei enter into prophase.

6. The results obtained have been compared with those obtained from a similar experiment involving the mouse testis. The accessory organs appear to be less sensitive to the irradiation than the testis. Factors bearing on this point are discussed.